Voltage sensing circuit capable of controlling a pump voltage stably generated in a low voltage environment

1. A voltage sensing circuit for sensing a level of a pumping voltage, comprising: a voltage dividing unit configured to divide a fed-back pumping voltage to output the divided pumping voltage; and a differential amplifier configured to perform differential amplification with a reference voltage as a first input and the divided pumping voltage as a second input, the differential amplifier having a source voltage at a negative voltage, wherein the pumping voltage is higher than a supply voltage and the negative voltage is lower than a ground voltage.

2. The voltage sensing circuit as recited in claim 1 , wherein the differential amplifier is a first differential amplifier, further comprising a second differential amplifier configured to perform differential amplification with an output of the first differential amplifier as a first input and the reference voltage as a second input.

3. The voltage sensing circuit as recited in claim 2 , further comprising a buffering unit configured to buffer an output of the second differential amplifier.

4. The voltage sensing circuit as recited in claim 2 , wherein the second differential amplifier has a current source that receives the negative voltage.

5. The voltage sensing circuit as recited in claim 1 , wherein the first differential amplifier includes: a current mirror having first and second terminals; a first switching element having a first current source, configured to control current on the first terminal of the current mirror by the reference voltage; a second switching element having a second current source, configured to control current from the second terminal of the current mirror in response to the divided pumping voltage; and a third switching element configured to control the first and second current sources respectively of the first and second switching elements to receive the negative voltage.

6. The voltage sensing circuit as recited in claim 5 , wherein the third switching element is connected between a current source common terminal of the first and second switching elements and the negative voltage.

7. A method of sensing a pumping voltage, comprising: dividing a fed-back pumping voltage to output a divided pumping voltage; and differentially amplifying a difference between the divided pumping voltage and a reference voltage using differential amplifiers which are supplied with a negative voltage as a source voltage, wherein the pumping voltage is higher than a supply voltage and the negative voltage is lower than a ground voltage.

8. The method as recited in claim 7 , wherein differentially amplifying the difference is performed through a plurality of amplifying steps, each amplifying step performed by each of the differential amplifiers.

9. The method as recited in claim 8 , wherein each amplifying step includes: controlling a first current on a first terminal of a current mirror by the reference voltage; controlling a second current from a second terminal of the current mirror in response to an output of the previous step; and outputting a differential amplified voltage according to the first and second currents.

10. The method as recited in claim 7 , further comprising buffering the result of differentially amplifying the difference.